Okay this is a PSA more than a question because I know the answer: January 13, 2011.
See: https://rhn.redhat.com/errata/RHEA-2011-0069.html
Colour me surprised though, didn't hear anything about in the blogosphere until I got a Security Errata notice today.
I have been using the REMI repo for this in the past but will switch over to the Red Hat blessed PHP 5.3.
Don't down-vote me bro! I'll select as the best answer the source that broke the news first (other than Red Hat of course). People have wanted this for so long I'm just amazed that it's finally happened!
Since 5.6
http://meetbot.fedoraproject.org/fedora-meeting/2009-09-11/fedora-meeting.2009-09-11-21.00.log.html
http://meetbot.fedoraproject.org/fedora-meeting-1/2010-02-27/fedora-meeting-1.2010-02-27-17.12.log.html